* Transparency to cover intergovernmental agreements
* Member states likely to oppose Brussels power grab
* Commission worried about Gazprom's dominance
BRUSSELS, Jan 26 (Reuters) - The EU wants the power to review energy deals between member states and countries such as Russia before they are signed, the bloc's top energy official said on Tuesday, a move opposed by some states reluctant to cede control to Brussels.
European Commission Vice-President Maros Sefcovic said the new powers for Brussels were a key part of draft energy security rules he intends to propose next month.
The energy security package aims to move the 28-member bloc towards a single energy union in which power and gas would flow freely across borders, reducing reliance on Russian gas.
"We are going to introduce this ex-ante check of the intergovernmental agreements," Sefcovic said.
"We should develop the mechanism where we would have the possibility to look into the intergovernmental agreements in a way that we would make sure that once concluded, they are compatible with EU law."
The web of deals Russia cut with Eastern European states to build the South Stream pipeline under the Black Sea morphed into a legal headache when the EU executive said it did not comply with rules on ownership or third-party pipeline access.
The oversight powers sought by the European Union would avoid the difficulty and complication of trying to renegotiate bilateral agreements after the fact, Sefcovic said.
He acknowledged overcoming objections from some member states may be "a complicated discussion".
Plans for pipelines to pump more Russian gas to Europe, including the expansion of the Nord Stream link to Germany, have pitted states who see it as a solution to supply disruptions via Ukraine against those worried about dependence on Russia.
Concerns about Russia's dominance have increased since Moscow's annexation of the Ukrainian region of Crimea.
Germany, which has negotiated successfully with Russia's Gazprom in the past, was opposed to greater EU transparency when the issue was debated by EU leaders in March.
Germany feared more transparency could lead to the disclosure of sensitive information whereas Poland, which pays higher gas prices, was in favour.
Gazprom, which supplies about a third of the EU's gas, mostly across Ukraine, is the target of an EU antitrust investigation for allegedly overcharging customers in Eastern Europe and thwarting rivals.
Gazprom declined to comment on the proposal. (Reporting by Alissa de Carbonnel; additional reporting by Katya Golubkova in Moscow; editing by David Clarke)